From patchwork Tue Jan 7 19:43:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lakshmi Ramasubramanian X-Patchwork-Id: 11321689 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DAF99138C for ; Tue, 7 Jan 2020 19:44:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A12E4214D8 for ; Tue, 7 Jan 2020 19:44:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="SL6AW4CD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728731AbgAGTn7 (ORCPT ); Tue, 7 Jan 2020 14:43:59 -0500 Received: from linux.microsoft.com ([13.77.154.182]:34234 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728607AbgAGTnz (ORCPT ); Tue, 7 Jan 2020 14:43:55 -0500 Received: from nramas-ThinkStation-P520.corp.microsoft.com (unknown [131.107.174.108]) by linux.microsoft.com (Postfix) with ESMTPSA id D28F320B479C; Tue, 7 Jan 2020 11:43:54 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com D28F320B479C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1578426234; bh=s+Zmgddx5AD2JWjCVm06VmtkMsj4CxUiQH6gDbhgmxQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SL6AW4CDhIAUptYWQwcTD7CFARyO6jxQXB1soIX08LDi+zEsj9a7lW52YaoYZLIsS dx28qbMroZLHVTQfX7Kr8EIzwxHujqe6keEoAEo8TB78uvlfoYmsgmQFZed+bscUO/ UoXc6uWiXMXHlY34M2EKClFXQK+tblCfu4fV5Wsk= From: Lakshmi Ramasubramanian To: zohar@linux.ibm.com, James.Bottomley@HansenPartnership.com, linux-integrity@vger.kernel.org Cc: eric.snowberg@oracle.com, dhowells@redhat.com, mathew.j.martineau@linux.intel.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org Subject: [PATCH 3/4] IMA: Add support to limit measuring keys Date: Tue, 7 Jan 2020 11:43:49 -0800 Message-Id: <20200107194350.3782-4-nramas@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200107194350.3782-1-nramas@linux.microsoft.com> References: <20200107194350.3782-1-nramas@linux.microsoft.com> Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org Limit measuring keys to those keys being loaded onto a given set of keyrings only and when the user id (uid) matches if uid is specified in the policy. This patch defines a new IMA policy option namely "keyrings=" that can be used to specify a set of keyrings. If this option is specified in the policy for "measure func=KEY_CHECK" then only the keys loaded onto a keyring given in the "keyrings=" option are measured. If uid is specified in the policy then the key is measured only if the current user id matches the one specified in the policy. Added a new parameter namely "keyring" (name of the keyring) to process_buffer_measurement(). The keyring name is passed to ima_get_action() to determine the required action. ima_match_rules() is updated to check keyring in the policy, if specified, for KEY_CHECK function. Signed-off-by: Lakshmi Ramasubramanian Fixes: e9085e0ad38a ("IMA: Add support to limit measuring keys") --- Documentation/ABI/testing/ima_policy | 10 +++- security/integrity/ima/ima.h | 8 ++- security/integrity/ima/ima_api.c | 8 ++- security/integrity/ima/ima_appraise.c | 4 +- security/integrity/ima/ima_asymmetric_keys.c | 8 ++- security/integrity/ima/ima_main.c | 9 +-- security/integrity/ima/ima_policy.c | 62 ++++++++++++++++++-- 7 files changed, 91 insertions(+), 18 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index 066d32797500..cd572912c593 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -25,7 +25,7 @@ Description: lsm: [[subj_user=] [subj_role=] [subj_type=] [obj_user=] [obj_role=] [obj_type=]] option: [[appraise_type=]] [template=] [permit_directio] - [appraise_flag=] + [appraise_flag=] [keyrings=] base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK] [FIRMWARE_CHECK] [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK] @@ -42,6 +42,9 @@ Description: appraise_flag:= [check_blacklist] Currently, blacklist check is only for files signed with appended signature. + keyrings:= list of keyrings + (eg, .builtin_trusted_keys|.ima). Only valid + when action is "measure" and func is KEY_CHECK. template:= name of a defined IMA template type (eg, ima-ng). Only valid when action is "measure". pcr:= decimal value @@ -117,3 +120,8 @@ Description: Example of measure rule using KEY_CHECK to measure all keys: measure func=KEY_CHECK + + Example of measure rule using KEY_CHECK to only measure + keys added to .builtin_trusted_keys or .ima keyring: + + measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index fe6c698617bd..f06238e41a7c 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -208,7 +208,8 @@ struct modsig; /* LIM API function definitions */ int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid, int mask, enum ima_hooks func, int *pcr, - struct ima_template_desc **template_desc); + struct ima_template_desc **template_desc, + const char *keyring); int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func); int ima_collect_measurement(struct integrity_iint_cache *iint, struct file *file, void *buf, loff_t size, @@ -220,7 +221,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file, struct ima_template_desc *template_desc); void process_buffer_measurement(const void *buf, int size, const char *eventname, enum ima_hooks func, - int pcr); + int pcr, const char *keyring); void ima_audit_measurement(struct integrity_iint_cache *iint, const unsigned char *filename); int ima_alloc_init_template(struct ima_event_data *event_data, @@ -235,7 +236,8 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename); /* IMA policy related functions */ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, enum ima_hooks func, int mask, int flags, int *pcr, - struct ima_template_desc **template_desc); + struct ima_template_desc **template_desc, + const char *keyring); void ima_init_policy(void); void ima_update_policy(void); void ima_update_policy_flag(void); diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c index 610759fe63b8..f6bc00914aa5 100644 --- a/security/integrity/ima/ima_api.c +++ b/security/integrity/ima/ima_api.c @@ -169,12 +169,13 @@ void ima_add_violation(struct file *file, const unsigned char *filename, * @func: caller identifier * @pcr: pointer filled in if matched measure policy sets pcr= * @template_desc: pointer filled in if matched measure policy sets template= + * @keyring: keyring name used to determine the action * * The policy is defined in terms of keypairs: * subj=, obj=, type=, func=, mask=, fsmagic= * subj,obj, and type: are LSM specific. * func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK - * | KEXEC_CMDLINE + * | KEXEC_CMDLINE | KEY_CHECK * mask: contains the permission mask * fsmagic: hex value * @@ -183,14 +184,15 @@ void ima_add_violation(struct file *file, const unsigned char *filename, */ int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid, int mask, enum ima_hooks func, int *pcr, - struct ima_template_desc **template_desc) + struct ima_template_desc **template_desc, + const char *keyring) { int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH; flags &= ima_policy_flag; return ima_match_policy(inode, cred, secid, func, mask, flags, pcr, - template_desc); + template_desc, keyring); } /* diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 300c8d2943c5..a9649b04b9f1 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -55,7 +55,7 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) security_task_getsecid(current, &secid); return ima_match_policy(inode, current_cred(), secid, func, mask, - IMA_APPRAISE | IMA_HASH, NULL, NULL); + IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL); } static int ima_fix_xattr(struct dentry *dentry, @@ -330,7 +330,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint, if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) process_buffer_measurement(digest, digestsize, "blacklisted-hash", NONE, - pcr); + pcr, NULL); } return rc; diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c index 994d89d58af9..fea2e7dd3b09 100644 --- a/security/integrity/ima/ima_asymmetric_keys.c +++ b/security/integrity/ima/ima_asymmetric_keys.c @@ -46,7 +46,13 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key, * parameter to process_buffer_measurement() and is set * in the "eventname" field in ima_event_data for * the key measurement IMA event. + * + * The name of the keyring is also passed in the "keyring" + * parameter to process_buffer_measurement() to check + * if the IMA policy is configured to measure a key linked + * to the given keyring. */ process_buffer_measurement(payload, payload_len, - keyring->description, KEY_CHECK, 0); + keyring->description, KEY_CHECK, 0, + keyring->description); } diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 9b35db2fc777..2272c3255c7d 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -215,7 +215,7 @@ static int process_measurement(struct file *file, const struct cred *cred, * Included is the appraise submask. */ action = ima_get_action(inode, cred, secid, mask, func, &pcr, - &template_desc); + &template_desc, NULL); violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) && (ima_policy_flag & IMA_MEASURE)); if (!action && !violation_check) @@ -632,12 +632,13 @@ int ima_load_data(enum kernel_load_data_id id) * @eventname: event name to be used for the buffer entry. * @func: IMA hook * @pcr: pcr to extend the measurement + * @keyring: keyring name to determine the action to be performed * * Based on policy, the buffer is measured into the ima log. */ void process_buffer_measurement(const void *buf, int size, const char *eventname, enum ima_hooks func, - int pcr) + int pcr, const char *keyring) { int ret = 0; struct ima_template_entry *entry = NULL; @@ -668,7 +669,7 @@ void process_buffer_measurement(const void *buf, int size, if (func) { security_task_getsecid(current, &secid); action = ima_get_action(NULL, current_cred(), secid, 0, func, - &pcr, &template); + &pcr, &template, keyring); if (!(action & IMA_MEASURE)) return; } @@ -721,7 +722,7 @@ void ima_kexec_cmdline(const void *buf, int size) { if (buf && size != 0) process_buffer_measurement(buf, size, "kexec-cmdline", - KEXEC_CMDLINE, 0); + KEXEC_CMDLINE, 0, NULL); } static int __init init_ima(void) diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 3f3928b3db99..7667ca546ce9 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -79,6 +79,7 @@ struct ima_rule_entry { int type; /* audit type */ } lsm[MAX_LSM_RULES]; char *fsname; + char *keyrings; /* Measure keys added to these keyrings */ struct ima_template_desc *template; }; @@ -356,6 +357,50 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event, return NOTIFY_OK; } +/** + * ima_match_keyring - determine whether the keyring matches the measure rule + * @rule: a pointer to a rule + * @keyring: name of the keyring to match against the measure rule + * @cred: a pointer to a credentials structure for user validation + * + * Returns true if keyring matches one in the rule, false otherwise. + */ +static bool ima_match_keyring(struct ima_rule_entry *rule, + const char *keyring, const struct cred *cred) +{ + char *keyrings, *next_keyring, *keyrings_ptr; + bool matched = false; + + if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid)) + return false; + + if (!rule->keyrings) + return true; + + if (!keyring) + return false; + + keyrings = kstrdup(rule->keyrings, GFP_KERNEL); + if (!keyrings) + return false; + + /* + * "keyrings=" is specified in the policy in the format below: + * keyrings=.builtin_trusted_keys|.ima|.evm + */ + keyrings_ptr = keyrings; + while ((next_keyring = strsep(&keyrings_ptr, "|")) != NULL) { + if (!strcmp(next_keyring, keyring)) { + matched = true; + break; + } + } + + kfree(keyrings); + + return matched; +} + /** * ima_match_rules - determine whether an inode matches the measure rule. * @rule: a pointer to a rule @@ -364,18 +409,23 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event, * @secid: the secid of the task to be validated * @func: LIM hook identifier * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) + * @keyring: keyring name to check in policy for KEY_CHECK func * * Returns true on rule match, false on failure. */ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, const struct cred *cred, u32 secid, - enum ima_hooks func, int mask) + enum ima_hooks func, int mask, + const char *keyring) { int i; if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) { - if ((rule->flags & IMA_FUNC) && (rule->func == func)) + if ((rule->flags & IMA_FUNC) && (rule->func == func)) { + if (func == KEY_CHECK) + return ima_match_keyring(rule, keyring, cred); return true; + } return false; } if ((rule->flags & IMA_FUNC) && @@ -479,6 +529,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func) * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) * @pcr: set the pcr to extend * @template_desc: the template that should be used for this rule + * @keyring: the keyring name, if given, to be used to check in the policy. + * keyring can be NULL if func is anything other than KEY_CHECK. * * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) * conditions. @@ -489,7 +541,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func) */ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, enum ima_hooks func, int mask, int flags, int *pcr, - struct ima_template_desc **template_desc) + struct ima_template_desc **template_desc, + const char *keyring) { struct ima_rule_entry *entry; int action = 0, actmask = flags | (flags << 1); @@ -503,7 +556,8 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, if (!(entry->action & actmask)) continue; - if (!ima_match_rules(entry, inode, cred, secid, func, mask)) + if (!ima_match_rules(entry, inode, cred, secid, func, mask, + keyring)) continue; action |= entry->flags & IMA_ACTION_FLAGS;